Some people believe that Kohnos guitars made from the mid 60s have better sound. These guitars generally have a 646-656mm scale length and mainly built by spruce tops, plus a variety of bracing patterns such as 5 and 7 fan. Also, Kohno won the international guitar building contest in 1967 which put him to everyone's radar.
He tended to build longer guitars (660mm) and reinforced necks with both spruce and cedar tops after the 70s. These guitars are often said to have a louder, more piano-like sound.